1. Field of the Invention
The present invention relates to an image processing system employed for edition processing such as layout processing of image data, and more particularly, it relates to an image processing system for expanding compressed binary or multilevel images before edition processing starting times.
2. Description of the Background Art
In relation to conventional prepress and printing steps, attempts have been positively made for improving the quality and saving the labor with development of units such as a scanner, a layout system, a computerized phototypesetter, an image data base and the like. Such units are still being actively developed, in order to further improve the function, reduce the cost and improve the operability.
On the other hand, an image processing system is also under active development, in order to construct a local area network (LAN) by connecting such units by a communication cable, compress/expand a large quantity of image data read by a scanner or the like, and electronize edition processing such as retouching, page make-up and layout operations. In particular, a technique of compressing image data, which serves as a key technology in such an image processing system, has been deeply studied, to make it possible to apply an international standardization system (Joint Photographic Expert Group) to printing as a compression system for binary and multilevel images. Thus, an image processing system which can compress and expand image data is now being put into practice.
However, a conventional image processing system has the following problem:
The conventional image processing system inevitably requires a skillful operator, who must manage overall image data processing in prepress steps. For example, the operator must decide image data compression/expansion schedules in relation to the times for compressing the image data, the times for expanding the compressed image data for transmitting the as-expanded image data to a layout system or the like, in image data compression/expansion processing on the basis of his knowledge and experience.
Thus, the operator has a heavy burden, while the compressed image data may be frequently expanded and continuously stored in an image data base considerably before times when the compressed image data are actually required for edition processing or the like. Thus, a large quantity of image data which are not yet necessary in time may occupy the image data base, to disadvantageously deteriorate the workability of the image processing system.
Such a problem arises not only in processing for compressing/expanding image data in the prepress steps, but also in the overall image processing system for compressing a large quantity of image data and thereafter processing the compressed image data at need.